In a power system in which commercial electric power is supplied to consumers, the power demanded by consumers varies depending on season and time. Accordingly, the maximum supply capacity of the power system is adjusted to the predicted maximum power demand, and when power demand does not reach the predicted maximum value, the power company adjusts electric power to be supplied, by reducing the number of generators to be operated, and/or operating the generators with lowered generation output.
However, maximum supply capacity is required several times a year. That is, the power company has to maintain a maximum supply capacity that will match the maximum value of power demand just for a few times each year and this has caused a problem in which the operation cost of the power system increases.
In contrast, a technology called demand response that controls the balance between supply and demand of electricity according to the need has drawn attention. For example, it is possible to avoid tight power supply and demand conditions by inducing consumers to reduce use of electricity in the time period when the power demand approaches the maximum capacity of the power system, in other words, when a tight balance between supply and demand of electricity is expected. More specifically, in the demand response, in the period during which power supply and demand conditions are tight, a power rate signal that indicates collection of a peak time electricity charge that is higher than the normal rate, a demand response signal that indicates a power saving command for requesting less use of electricity, or the like, are given to consumers so as to induce the consumers to change the set temperature of air conditioners and/or the brightness of lighting apparatus to thereby suppress power consumption. Since use of demand response makes it possible to avoid tight power supply and demand conditions even if the maximum supply capacity is lowered, it is possible to reduce the operating cost of the power system.
However, in the demand response, consumers need to lower the power consumption of electric appliances such as air conditions, lighting apparatus and the like. Lowering power consumption means that it is not possible to maintain a comfortable temperature and not possible to maintain room brightness which reduces consumer comfort in most cases. For this reason, consumers tend to give priority to comfort and neglect using demand response or stop using demand response partway, so that the stability of the power system ends up being lost.
Further, with the recent spread of electric vehicles and power generation equipment such as solar power generation installed in individual consumer's home, consumers who own storage batteries have increased in number. Such storage batteries are used to temporarily store the power generated by solar power generation so that stored power can be used during times when electricity is not generated, or are used to store commercial electricity during time when the electricity rate is low so as to use stored power during time when the electricity rate is high.
For example, Patent Document 1 discloses a technology in which a charging control apparatus for controlling charging of storage batteries selects time periods for charging storage batteries based on the consumption condition of the electricity stored in storage batteries and/or the electricity rate in each time period, to thereby charge the storage batteries in a systematic manner.